A three chamber flow-mix calorimeter fabricated at the Biocalorimetry Center is being re-designed with enhanced sensitivity and rapid thermostatting capabilities for operation over a broad temperature range. The major design modifications include installation of a new calorimetric block and modified electronic control board. These improvements will result in a high-sensitivity flow-mix calorimeter affording rapid measurement of binding enthalpies as a function of temperature for low reactant volumes and/or dilution factors.